Retinal pigment epithelial cells are highly specialized phagocytic cells which remove discarded photoreceptor outer segments during the normal visual process. Preliminary studies designed to investigate the recognition signals which trigger phagocytosis of shed, but not intact, outer segments have led to the hypothesis that there are mannosyl residues of glycoproteins of the shed segments which are recognized by mannose receptors on the epithelial cell surfaces, and that this mannose-recognition system is the basis for the receptor-mediated endocytosis. This research is designed to investigate this hypothesis directly. This work will elucidate the normal mechanism whereby the eye naturally disposes of the used, discarded photoreceptor outer segments which would otherwise accumulate in the eye.
